title: Plasma osteopontin is a useful diagnostic biomarker for advanced non-small cell lung cancer.
abstract: BACKGROUND
  Osteopontin (OPN) and carbonic anhydrase IX (CAIX), which are expressed on the surface of tumor cells, are associated with hypoxia during tumor development and progression. However, the roles of these proteins in the plasma of patients with non-small cell lung cancer (NSCLC) are poorly understood. Herein, we hypothesized that plasma OPN and CAIX levels could be used as diagnostic and prognostic tumor markers in patients with NSCLC.
  
  
  METHODS
  Fifty-three patients with NSCLC and 50 healthy control subjects were enrolled. We selected controls without malignancy and matched them with NSCLC patient cases according to age and gender. Blood samples were collected at the time of diagnosis; the plasma levels of OPN and CAIX were measured by enzyme-linked immunosorbent assays.
  
  
  RESULTS
  The plasma levels of OPN in the patients with NSCLC were significantly elevated as compared to those in the controls (p=0.016). However, there was no difference in the plasma level of CAIX between the NSCLC patients and controls. NSCLC patients with a distant metastasis had a remarkable increase in plasma OPN compared with patients without metastasis (p=0.026), but no such correlation was found for CAIX. There was no difference in overall survival rates according to the plasma level of OPN between the two groups (by Kaplan-Meier survival analysis).
  
  
  CONCLUSIONS
  Plasma OPN levels were elevated in patients with NSCLC as compared with the controls, with greater elevation of OPN levels in the advanced stages of disease. Therefore, plasma OPN may have utility as a diagnostic, but not prognostic, biomarker of advanced NSCLC.
authors.affiliation: Department of Internal Medicine, Kangwon National University School of Medicine, Chuncheon, Korea.
authors.forename: Seon-Sook
authors.initials: SS
authors.lastname: Han
authors.forename: Seung-Joon
authors.initials: SJ
authors.lastname: Lee
authors.forename: Woo Jin
authors.initials: WJ
authors.lastname: Kim
authors.forename: Dong Ryeol
authors.initials: DR
authors.lastname: Ryu
authors.forename: Jun Yeon
authors.initials: JY
authors.lastname: Won
authors.forename: Shinyoung
authors.initials: S
authors.lastname: Park
authors.forename: Myeong Ju
authors.initials: MJ
authors.lastname: Cheon
keywords: CA9 Protein, Human; Lung Neoplasms; Osteopontin